Chemically Stable Metal-Organic Frameworks: Rational Construction and Application Expansion

Ion incorporation into cobalt(II)-organic framework for green and efficient synthesis of oxazolidinones via carbon dioxide fixation

Developing a green and efficient method for CO2 transformation is crucial for advancing carbon neutrality and effective resource utilization. Among the transformations, carboxylative cyclization of CO2 to produce oxazolidinones is an atom-economical reaction with valuable pharmaceutical applications. However, most catalytic systems often require high temperatures, organic solvents or show low efficiency. Herein, we report a novel anionic framework, {[NH2(CH3)2]2[Co3(L)3(µ3-O)]·0.37DMA }n (1), which can be synthesized on a gram scale and displays excellent stability. As a catalyst, compound 1 enables the carboxylative cyclization of propargylic amines with CO2 at 70 °C for 12 h under ambient pressure, and can be reused up to 10 times while maintaining structural stability. Given the relatively high temperature and extended reaction time required in the 1-catalytic system, Ag+ and Cu2+ ions are incorporated into the framework of compound 1 through cation exchange. The Ag+-incorporated composite 1-Ag(0.05) exhibits high catalytic efficiency under ambient temperature and CO2 pressure within 6 h without using solvent, and can be reused for at least five successive cycles. Control experiments and DFT calculations reveal that the synergistic interaction between Ag+, Co-framework and DBU is the key factor promoting the reaction. To our knowledge, this study provides the first comprehensive investigation into the impact of ion incorporation on the catalytic performance of a Co-based framework in the carboxylative cyclization of propargylic amines with CO2.

MOF composites for revolutionizing blue energy harvesting and next-gen soft electronics

Metal-organic frameworks (MOFs) are porous materials with highly ordered and crystalline structures, which have earned tremendous attention in the academic community in recent years owing to their high tunability in porosity and pore structure. By integrating MOFs with soft colloids or polymers to form MOF composites, the rigidity and brittle nature of MOFs can be compensated for, thus achieving synergistic effects for a wide variety of applications. In particular, the past decade has seen the advancement of MOF composites in the budding fields of blue energy harvesting and soft electronics, which have received growing interest in the past 5 years. This review focuses on the applications of MOF composites in these two fields, and starts by examining the nanoarchitectures of MOFs, followed by the fabrication of MOF composites. Furthermore, topical advances of MOF composites in blue energy harvesting and soft electronics are reviewed and summarized, and their challenges and future opportunities are discussed as the final touch. This article provides comprehensive review and valuable insights into the development of MOF composites, which may open up new avenues for blue energy harvesting and soft electronics to solve the imminent energy crisis and to advance the wearable technology in healthcare.

MOF-based nanomaterials for advanced aqueous-ion batteries

Metal-organic frameworks (MOFs)-based nanomaterials have great potential in the field of electrochemical energy storage due to their abundant pore size, high specific surface area, controllable structure and porosity, and homogeneous metal center. MOFs complexes and derivatives not only inherit the original morphology characteristics of MOFs but also provide excellent electrochemical performance. Batteries operating in aqueous electrolytes are cheaper, safer, and have higher ionic conductivity than those operating in conventional organic electrolytes. Therefore, it is useful to summarize the MOFs that should be used for aqueous electrochemical energy storage devices. This manuscript firstly introduces the composition and energy storage mechanism of aqueous Li/Na/Zn ion batteries. In addition, a detailed review of the development of MOFs-based nanomaterials and their commonly used characterization under aqueous conditions is presented. The relationship between the structure and composites of MOFs-based nanomaterials and electrochemical performance is highlighted. The applications of MOFs composites in aqueous batteries in terms of electrode materials and electrolytes are presented and summarized. Finally, research directions and perspectives for MOFs-based nanomaterials in advanced aqueous batteries are presented.

CuNi-PTC metal-organic framework: unveiling pseudocapacitive energy storage and water splitting capabilities

Metal-organic frameworks (MOFs), owing to their distinctive structural properties and customizable functionalities, have been garnering significant attention in the pursuit of advanced energy storage and conversion technologies. In this work, a bimetallic MOF, CuNi-PTC, has been synthesized through a straightforward method. Investigations reveal its potential as a high-performance electrode material for supercapacitors and as an electrocatalyst for water splitting. The CuNi-PTC MOF features a large specific surface area, hierarchical porosity, and strong structural stability, as evidenced by spectroscopic and electron microscopy analyses. As a supercapacitor electrode material, CuNi-PTC delivers an impressive specific capacitance of 1066.24 F g-1 at a current density of 1 A g-1, along with excellent cycling stability, retaining 94% of its capacity after 5000 charge-discharge cycles. Additionally, the electrocatalytic performance of CuNi-PTC for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) was assessed, showing overpotentials of 212 mV for the HER and 380 mV for the OER at a current density of 10 mA cm-2, along with exceptional long-term durability.

Morphology Engineering of Zr-N MOFs for High-Efficiency Photocatalytic Hydrogen Evolution

Metal-organic frameworks (MOFs) show promise in photocatalytic hydrogen evolution due to their intrinsic porosity and structural tunability, but their performance is often limited by poor reactant diffusion and slow charge transfer. In this paper, we obtained the UiO-68-NH2 (Zr-N) MOF with flake, octahedron, block, and flower morphologies in different sizes by adjusting the concentrations of acetic acid and water modulators. It is disclosed that the introduced acetic acid can compete with organic ligands for coordination with zirconium nodes, whereas water can affect the hydrolysis rate of zirconium precursors, thereby regulating the nucleation and crystal growth of the Zr-N crystals. Therefore, their synergistic effect led to the successful synthesis of Zr-N ions with different morphologies and sizes. Notably, the flower-like Zr-N with a size of about 100 nm and maximum specific surface area exposure of abundant active sites, which facilitates the diffusion of reactants as well as enhances the separation and transfer rate of photogenerated carriers, endowing it with excellent hydrogen evolution performance (989 μmol g-1 h-1) and being about 75 times higher than that of the bulk Zr-N counterpart (13 μmol g-1 h-1). This work validates the critical role of morphology engineering in advancing MOF-based photocatalysts for sustainable energy applications.

An ionic ultramicroporous polymer with engineered nanopores enables enhanced acetylene/carbon dioxide separation

A nanopore engineering approach enhances acetylene (C2H2) over carbon dioxide (CO2) selectivity in ionic ultramicroporous polymers (IUPs), an understudied class of sorbents. Extending the cationic arm of a prototypical IUP nearly doubles its C2H2/CO2 selectivity from 4.9 to 8.5 (at 298 K, 1 bar), underpinned by further observations from dynamic separation experiments and bespoke computational insights.

Aqueous-Phase Synthesis of Cyclic Trinuclear Cluster-Based Metal-Organic Frameworks

The synthesis of metal-organic frameworks (MOFs) often involves high-boiling-point organic solvents, which can have extensive environmental impact and limit their large-scale applications. Here, we present a one-pot aqueous-phase approach for the rapid preparation of 33 trinuclear-copper-cluster-based MOFs (1 to 33) with different pyrazoles under ultrasonic irradiation. To address the water-solubility challenge of organic linkers, we employ aromatic amines/aldehydes and pyrazole aldehydes/amines to in situ generate imine-based pyrazoles. This linker dismantling strategy enables the formation of low-concentration pyrazoles, which are essential for the assembly of trinuclear-copper-cluster-based MOFs in the aqueous phase. The use of preassembled trinuclear gold complexes instead of aromatic amines affords an Au-Cu-based MOF (34) of alternating gold and copper clusters, a rare example of MOFs with mixed yet precise arrangement of metal compositions. Additionally, the direct addition of pyruvic acid to the reaction mixture results in the facile synthesis of a carboxylic-acid-functionalized MOF (35), eliminating the need for preinstallation or postmodification steps in traditional MOF synthesis. Furthermore, we demonstrate 11-AA as an efficient photocatalyst for cross-dehydrogenative coupling (CDC) reactions, exploiting the synergetic effect of substrate activation on the copper sites and subsequent coupling initiated by the photosensitive organic linkers. This work offers a simple solution for making MOFs with minimal environmental impact; it also opens up possibilities for developing multifunctional MOFs for diverse applications.

Self-sacrificial synthesis of Cu3(HHTP)2 on Cu substrate for recyclable NH3 gas adsorption with energy-efficient photothermal regeneration

The efficient adsorption and removal of toxic gases, particularly ammonia (NH3), remains a critical challenge in environmental management and industrial safety. Metal-organic frameworks (MOFs) have emerged as promising gas adsorbents due to their tunable structures and high surface area. However, the strong interaction between NH3 and MOFs poses challenges for the regeneration and reusability of MOF adsorbents, often requiring energy-intensive desorption methods. This study proposes a sustainable approach for regenerating adsorption sites for recyclable gas adsorbents. We present a facile method for the direct synthesis of Cu3(HHTP)2 on a Cu mesh substrate (Cu3(HHTP)2@Cu), utilizing the Cu metal itself as a precursor to eliminate the need for external metal sources. The resulting Cu3(HHTP)2@Cu serves as a recyclable NH3 adsorbent, leveraging the π-conjugated hexahydroxytriphenylene (HHTP) ligand for photothermal conversion under sunlight irradiation, where photo-generated heat facilitates NH3 desorption. The study further explores the effect of an external voltage on the NH3 adsorption performance and crystalline structure of Cu3(HHTP)2@Cu. Our findings demonstrate that Cu3(HHTP)2@Cu achieves efficient NH3 desorption through a minimally invasive and energy-efficient mechanism, addressing the limitations of conventional adsorbents.

Efficient Hg(Ⅱ) removed by l-cysteine modified UiO-66 through chemical adsorption via a facile partial ligand replacement strategy

In this work, UiO-66-l-cys with enhanced adsorption capacity for Hg(Ⅱ) in water was synthesized through a facile two-step partial ligand replacement strategy. The presence of the functional groups significantly enhanced the capacity of the material for Hg(Ⅱ). According to the Langmuir model, the maximum theoretical adsorption capacity was calculated to be 1321.4 mg/g, which is 20 times that of the original UiO-66. Thermodynamic study revealed that the adsorption of Hg(II) onto UiO-66-l-cys is a spontaneous and endothermic process, thus exhibiting an elevated adsorption capacity at higher temperatures. XPS results confirmed that the sulfhydryl (SH) and amino (NH2) groups react with Hg(Ⅱ), enabling the material to adsorb a large quantity of Hg(Ⅱ). Through DFT theoretical calculation and simulation, it has been found that S atoms and N atoms exhibit significant attraction to Hg atoms. Moreover, the corrosion potential of UiO-66 in Hg solution becomes lower. It is demonstrated that it has a faster electron transfer rate, which is conducive to the adsorption process. Furthermore, UiO-66-l-cys exhibited an excellent cyclic stability, with only a 2.7 % decrease in adsorption capacity after five cycles. This method eliminates the necessity for the pre-synthesis of complex chemical ligands and intricate chemical reactions. It also streamlines the process, and lowers material costs. The UiO-66-l-cys exhibits considerable potential applications for the treatment of heavy metal pollution.

Metal pyrazolate frameworks: crystal engineering access to stable functional materials

As the focus evolves from structure discovery/characterization (what it is) to property/performance exploration (what it is for), the pursuit of stable functional metal-organic frameworks (MOFs) has been ongoing in terms of both fundamental research and industrial implementation. Under the guidance of crystal engineering principles, a plethora of research has developed pyrazolate MOFs (metal pyrazaolate frameworks, MPFs) featuring strong coordination M-N bonding. This attribution helps them retain their structures and functions under the alkaline conditions required for practical use. Based on poly-topic pyrazolate ligands, various classic MOFs, such as Co(bdp), Fe2(BDP)3, Ni8L6, PCN-601, and BUT-55, to name a few, have revealed fascinating architectures, intriguing properties, and record-breaking performances in applications during the past decade. This review will present the full scope of MPFs to date: (1) the superiority and significance of constructing MPFs through the crystal engineering approach, (2) synthetic strategies adopted in building and/or modifying MPFs, (3) structural features and stability of the MPF community, and (4) potential applications in energy and environmental related fields. The future opportunities of MPFs are also discussed for designing the next-generation of smart materials. Overall, this review attempts to provide insights and guidelines for the customization of pyrazolate-based MOFs for specific purposes, which would also promote the development of stable functional porous materials for addressing societal challenges.

Water-Stable MIL-MOFs Developed Through a Novel Sacrifice-Protection Strategy Inspired by Butterfly Wings' Scales for Long-Term Turn-On Fluorescence Sensing of H2S

Metal-organic frameworks, which are the desired candidates for biosensing application due to their tunable properties, are significantly hindered by their rapid degradation in aqueous solutions, as well as the loss of their inherent fluorescence. Most studies aim to improve the hydrophobicity of materials by modifying their contact angle, thereby enhancing water stability. However, water droplets poorly adhere to the surface of hydrophobic materials, limiting their application for direct contact and detection in aqueous environments. Drawing inspiration from the sacrificial protection mechanism of butterfly wings used to evade predation and entanglement, a universal approach is successfully developed to protect water-sensitive MIL-MOFs from water molecule attack while preserving good hydrophilicity. Using the organic ligand 2,2'-bipyridine-5,5'-dicarboxylic acid (bpydc) as sacrificial protection scales, the MIL-125-NH2-bpydc demonstrated broad pH structural stability (pH 2-12) and fluorescence stability increased by 10.17 time in aqueous solutions, achieving the highest performance in MILMOFs. The MIL-125-NH2-bpydc is biocompatible enabling it to perform long-term fluorescence imaging in living cells and zebrafish, further detecting hydrogen sulfide (H2S) in the aqueous and biological systems via turn-on fluorescence emission. This study offers a novel and universal sacrifice-protection strategy for the design and development of the luminescent biocompatible MOFs tailored for biosensing applications.

Silver Nanoparticles Decorated UiO-66-NH2 Metal-Organic Framework for Combination Therapy in Cancer Treatment

Background: Nanomedicine has shown significant promise in advancing cancer diagnostics and therapeutics. In particular, nanoparticles (NPs) offer potential for overcoming limitations associated with conventional therapies, such as off-target toxicity and side effects. Among the various NPs, silver nanoparticles (AgNPs) have garnered attention due to their cytotoxic and genotoxic properties in cancer cells. However, despite their potential, the optimization of AgNPs efficacy often necessitates combination strategies with other therapeutic agents. This study explores the potential of AgNPs integrated with Zr-based metal-organic frameworks (MOFs) UiO-66 for drug delivery, to enhance cancer therapy. Methods: We decorated amino-terephthalic based UiO-66-NH2 with AgNPs and loaded it with the chemotherapeutic agent cisplatin (Cis-Pt) to make the UiO-66-NH2@AgNPs@Cis-Pt. A preliminary MTT assay was conducted to evaluate the cytotoxic effects of the nanocomposite on several glioblastoma and other tumour cell lines, including U251, U87, GL261, HeLa, RKO, and HepG2. Results: Our results demonstrate that UiO-66-NH2@AgNPs@Cis-Pt and its combinations exhibit enhanced cytotoxicity compared to individual components such as AgNPs and Cis-Pt. Conclusions: This work offers preliminary insights into the potential of AgNP-functionalized MOFs as effective drug and delivery platforms, particularly in the context of combination therapy for cancer treatment.

Post-Modification of MOF with Electron Donor for Efficient Photocatalytic Oxidative Organic Transformations

Construction of donor-accepter systems via self-assembling electron donor and acceptor chromophores within one single metal-organic framework (MOF) for advanced artificial photosynthesis is of great intertest yet a major challenge. Herein, an electron donor porphyrin 5-(4-carboxyphenyl)-10,15,20-triphenylporphyrin (PCOOH) was successfully integrated into a highly stable and porous electron acceptor naphthalene diimide (NDI)-based MOF (Zr-NDI) through the postmodified approach of solvent-assisted ligand incorporation (SALI). Benefiting from the efficient photoinduced electron transfer (PET) from the donor PCOOH anchored on the Zr-nodes to the acceptor NDI ligand, which contributes to the abundant generation of reactive oxygen species (ROS) of superoxide radical (O2 •-), the resulting MOF Zr-NDI-PCOOH exhibited superior photocatalytic activities that among the highest levels of MOF-based photocatalysts to aerobic oxidation reactions, including hydroxylation of arylboronic acids and homocoupling of amines. This work exemplifies an avenue to develop high-efficiency MOF-based donor-acceptor systems for advanced artificial photosynthesis through facile post-modified approach.

Metal-Organic Frameworks (MOFs): Multifunctional Platforms for Environmental Sustainability

Metal-Organic Frameworks (MOFs) have emerged as versatile materials bridging inorganic and organic chemistry to address critical environmental challenges. Composed of metal nodes and organic linkers, these crystalline structures offer unique properties such as high surface area, tunable pore sizes, and structural diversity. Recent advancements in MOFs synthesis, particularly innovative approaches like mechanochemical, microwave-assisted, and ultrasonic synthesis, have significantly enhanced sustainability by utilizing non-toxic solvents, renewable feedstocks, and energy-efficient processes, offering promising solutions to reduce environmental impact. This review highlights these novel methods and their contributions to improving MOFs functionality for applications in environmental remediation, gas capture, and energy storage. We examine the potential of MOFs in catalysis for pollutant degradation, water purification, and hazardous waste removal, as well as their role in next-generation energy storage technologies, such as supercapacitors, batteries, and hydrogen production. Furthermore, we address challenges including scalability, stability, and long-term performance, underscoring the need for continued innovation in synthesis techniques to enable large-scale MOFs applications. Overall, MOFs hold transformative potential as multifunctional materials, and advancements in synthesis and sustainability are critical for their successful integration into practical environmental and energy solutions.

Formation of polysulfides as a smart strategy to selectively detect H2S in a Bi(iii)-based MOF material

SU-101 was demonstrated to be an effective and efficient detector for H2S, due to the facile generation of polysulfides, with a remarkable H2S selectivity. Raman and XPS analyses confirmed the formation of S n 2- and S4 2- polysulfide species after the H2S adsorption (at 0.05 bar, 0.1 bar and 1 bar), without compromising the structural integrity of SU-101. The detection mechanism involves rigidification of the structure by the formation of the polysulfides and blockage of the ligand-metal charge transfer (LMCT) process, which increased the radiative emission. Additionally, theoretical simulations were carried out in order to demonstrate that the interaction of the polysulfide molecules inside the pores of SU-101 is energetically stable. Remarkably, the limit of H2S detection (LOD) was calculated to be as low as approximately 22 ppm. Finally, SU-101 is nominated as a promising candidate for implementing toxic waste valorisation (i.e., capture of toxic H2S) toward relevant applications in accurate molecular sensing.

Construction of robust Cu-MOFs from bifunctional pyridine-hydroxamate linkers for photocatalytic CO2 reduction

Robust Cu-MOFs with distinct topologies were prepared from the same bifunctional 4-pyridine-hydroxamate ligand. A favourable collection of porosity, framework stability, electronic structure, and photochemical properties was revealed for the SUM-33 MOF, which was later experimentally verified as an efficient and selective photocatalyst for CO2-to-CO conversion.

Covalent Metal-Organic Frameworks: Fusion of Covalent Organic Frameworks and Metal-Organic Frameworks

ConspectusMetal-organic frameworks (MOFs) and covalent organic frameworks (COFs), as emerging porous crystalline materials, have attracted remarkable attention in chemistry, physics, and materials science. MOFs are constructed by metal clusters (or ions) and organic linkers through coordination bonds, while COFs are prepared by pure organic building blocks via covalent bonds. Because of the nature of linkages, MOFs and COFs have their own shortcomings. Typically, the relatively weak bond strengths of coordination bonds lead to poor chemical stability of MOFs, which limits their practical implementations. On the other hand, due to the strong covalent bonds, COFs exhibit rather higher stability under harsh conditions, compared to MOFs. However, the lack of open metal sites restricts their functionalization and application. Therefore, it is hypothesized that the "cream-skimming" of MOFs and COFs would address these drawbacks and produce a new class of crystalline porous material, namely, covalent metal-organic frameworks (CMOFs), with unprecedented structural complexity and advanced functionality. The CMOFs reveal a new synthetic approach for the preparation of reticular materials. Specifically, metal ions are reacted with chelating ligands to assemble metal complexes or clusters with functional reactive sites (e.g., -CHO, and -NH2), which can be further connected with organic linkers to form networked structures via dynamic covalent chemistry (DCC). The isolated metal complex or cluster precursors show enhanced stability which prevents structural decomposition and rearrangements during the self-assembly process of CMOFs. Since the topology of preassembled metal nodes is well-defined, the CMOFs structure can be readily predicted upon directed networking of covalent bonds. Unaccessible reticular materials from unstable or highly reactive metal ion/clusters under traditional conditions can be prepared via the DCC approach. Moreover, CMOFs synergize the advantages of MOFs and COFs, containing metal active sites ensuring various interesting properties, and covalent linkages that allow rather high chemical stability even under harsh conditions. In the past few years, our group has specifically focused on the development of general synthetic strategies for CMOFs by networking coinage metal (Cu, Ag, and Au)-based cyclic trinuclear units (CTUs) with DCC. The CTUs exhibit trigonal planar structures and can be functionalized with reactive sites, such as -NH2 and -CHO, that can further react with organic linkers to afford CMOFs. Notably, CTUs also features interesting properties including metallophilic attraction, π-acidity/basicity, luminescence, redox activity and catalytic activity, which can be incorporated into CMOFs. Therefore, we envision that CMOFs would be promising platforms not only for the development of novel reticular materials, but also for potential applications in many research fields including gas absorption/separation, sensing, full-color display, catalysis, energy, and biological applications. In this Account, we summarize the recent studies on CMOFs, starting with linkage and topological design, structural transformation, morphological control, and potential applications in various fields. We also discuss the future opportunities and challenges in this rapidly developed research field of CMOFs. We hope this Account may promote new scientific discoveries and further development of CMOF-based materials and technologies in the future.

Synergistic Enhancement of Ligand & Cluster Connectivity to Construct Highly Stable Fluorescein-Based MOFs with Thickened Channel Walls for Boosting Photocatalytic Activity

Fabricating visible-light-responsive metal-organic frameworks (MOFs) with high stability and effective catalytic functionality remains a long-term pursuit yet a great challenge. Herein, a strategy of increasing ligand and cluster connectivity is developed to construct highly stable fluorescein MOFs, La-CFL, presenting a new (4,8)-connected topological structure compared to Cd-FL constructed using 6-connected dinuclear clusters and 3-connected tritopic ligands. La8(CFL)4 containers like Chinese "Ritual Wine Vessels (Jue)" resemble linear arrangements interconnected by the [La2(COO)4] clusters. This arrangement induces benzene rings and xanthene rings to locate on the inner walls of 1D channels, resulting in thicker channel walls that contribute to enhanced stability. Consequently, La-CFL demonstrates outstanding catalytic performance in thiol-ene reactions under green LED irradiation. It exhibits 2.3 times higher efficiency than Cd-FL while reducing reaction time to one-fifth at 20 min. Furthermore, La-CFL displays size-selective catalysis and retains full activity for 20 cycles without degradation, an improvement over Cd-FL's recyclability limitations.

Chemical Design of Magnetic Nanomaterials for Imaging and Ferroptosis-Based Cancer Therapy

Ferroptosis, an iron-dependent form of regulatory cell death, has garnered significant interest as a therapeutic target in cancer treatment due to its distinct characteristics, including lipid peroxide generation and redox imbalance. However, its clinical application in oncology is currently limited by issues such as suboptimal efficacy and potential off-target effects. The advent of nanotechnology has provided a new way for overcoming these challenges through the development of activatable magnetic nanoparticles (MNPs). These innovative MNPs are designed to improve the specificity and efficacy of ferroptosis induction. This Review delves into the chemical and biological principles guiding the design of MNPs for ferroptosis-based cancer therapies and imaging-guided therapies. It discusses the regulatory mechanisms and biological attributes of ferroptosis, the chemical composition of MNPs, their mechanism of action as ferroptosis inducers, and their integration with advanced imaging techniques for therapeutic monitoring. Additionally, we examine the convergence of ferroptosis with other therapeutic strategies, including chemodynamic therapy, photothermal therapy, photodynamic therapy, sonodynamic therapy, and immunotherapy, within the context of nanomedicine strategies utilizing MNPs. This Review highlights the potential of these multifunctional MNPs to surpass the limitations of conventional treatments, envisioning a future of drug-resistance-free, precision diagnostics and ferroptosis-based therapies for treating recalcitrant cancers.

Tailorable Ionic Frameworks for Selective Gas Adsorption and Separation: Bridging Experimental Insights with Mechanistic Understanding

The selective adsorption and separation of gases using solid adsorbents represent a crucial method for the treatment of toxic gases and the preparation of high-purity gases. The interaction forces between gas molecules and solid adsorbents are influenced by various factors, making precise design of adsorbents to achieve specific gas adsorption a pressing issue that requires urgent attention. In this study, a series of ionic frameworks constructed from Na+ and polyoxometalates (POMs) have been constructed through ionic interactions, and possess multiple adjustable parameters. These frameworks exhibit 3D open channels and demonstrate excellent thermal, humidity, and solvent stability. The synthesized ionic frameworks show strong adsorption capabilities for polar gas molecules such as SO2 and NH3, while exhibiting negligible adsorption for nonpolar or weakly polar gases like CO, O2, CH4, N2, and H2, thereby highlighting their significant gas selectivity. Theoretical calculations reveal that the interaction strength between the ionic frameworks and the polar gases is substantially stronger than that for other gaseous species, corroborating the experimental findings. This research not only provides a series of effective absorbents for polar gases but also elucidates key influencing factors on gas adsorption process, thereby inspiring new directions in the development of innovative gas adsorbents.

Pore Chemical Modification of Bimetallic Coordination Networks for Coal-Bed Methane Purification under Humid Conditions

The recycling of low-concentration coal-bed methane (CBM) is environmentally beneficial and plays a crucial role in optimizing the energy mix. In this work, we present a strategy involving pore chemical modification to synthesize a series of bimetallic diamond coordination networks, namely CuIn(ina)4, CuIn(3-ain)4, and CuIn(3-Fina)4 (where ina = isonicotinic acid, 3-ain = 3-amino-isonicotinic acid, and 3-Fina = 3-fluoroisonicotinic acid). Among these, the amino-functionalized CuIn(3-ain)4 exhibits excellent CH4 adsorption capacity (1.71 mmol g-1) and CH4/N2 selectivity (7.5) due to its optimal pore size and chemical environment, establishing it as a new benchmark material for CBM separation. Dynamic breakthrough experiments confirm the exceptional CH4/N2 separation performance of CuIn(3-ain)4. Notably, CuIn(3-ain)4 demonstrates excellent stability under wet conditions and maintains outstanding separation performance even in high-humidity environments. Additionally, theoretical simulations provide valuable insights into how selective adsorption performance can be fine-tuned by manipulating the pore size and geometry. Regeneration tests and cycling evaluations further underscore the remarkable potential of CuIn(3-ain)4 as a highly efficient adsorbent for the separation of CBM.

Spiral-Concave Prussian Blue Crystals with Rich Steps: Growth Mechanism and Coordination Regulation

Investigating the formation and transformation mechanisms of spiral-concave crystals holds significant potential for advancing innovative material design and comprehension. We examined the kinetics-controlled nucleation and growth mechanisms of Prussian Blue crystals with spiral concave structures, and constructed a detailed crystal growth phase diagram. The spiral-concave hexacyanoferrate (SC-HCF) crystals, characterized by high-density surface steps and a low stress-strain architecture, exhibit enhanced activity due to their facile interaction with reactants. Notably, the coordination environment of SC-HCF can be precisely modulated by the introduction of diverse metals. Utilizing X-ray absorption fine structure spectroscopy and in situ ultraviolet-visible spectroscopy, we elucidated the formation mechanism of SC-HCF to Co-HCF facilitated by oriented adsorption-ion exchange (OA-IE) process. Both experimental data, and density functional theory confirm that Co-HCF possesses an optimized energy band structure, capable of adjusting the local electronic environment and enhancing the performance of the oxygen evolution reaction. This work not only elucidates the formation mechanism and coordination regulation for rich steps HCF, but also offers a novel perspective for constructing nanocrystals with intricate spiral-concave structures.

Understanding water reaction pathways to control the hydrolytic reactivity of a Zn metal-organic framework

Metal-organic frameworks (MOFs) are a class of porous materials that are of topical interest for their utility in water-related applications. Nevertheless, molecular-level insight into water-MOF interactions and MOF hydrolytic reactivity remains understudied. Herein, we report two hydrolytic pathways leading to either structural stability or framework decomposition of a MOF (ZnMOF-1). The two distinct ZnMOF-1 water reaction pathways are linked to the diffusion rate of incorporated guest dimethylformamide (DMF) molecules: slow diffusion of DMF triggers evolution of the initial MOF into a water-stable MOF product exhibiting enhanced water adsorption, while fast exchange of DMF with water leads to decomposition. The starting MOF, three intermediates from the water reaction pathways and the final stable MOF have been characterized. The documentation of two distinct pathways counters the stereotype that water exposure always leads to destruction or degradation of water-sensitive MOFs, and demonstrates that water-stable MOFs with improved adsorption properties can be prepared via controlled solvent-triggered structural rearrangement.

Chrome-free leather processing based on amine pendant metal-organic frameworks and dialdehyde with enhanced dye affinity

To overcome the stringent regulations in the usage of chromium salts and dye-rich effluent let out by the tanning industry, a sustainable way of leather processing has been demonstrated utilizing amine pendant metal-organic frameworks (MOF) UiO-66-NH2 along with glyoxal. It was found that an offer of 8% (w/w) MOF along with 6% (w/w) glyoxal increased the shrinkage temperature of the leathers to 89 ± 2 °C with exhaustion of MOF up to 84.3 ± 1.5%. The presence of cationic amine sites in the MOF aided in the fixation of anionic post-tanning agents and improved the adsorption of dyes from 74.3 ± 2.5% in the case of conventional leather to 91.8 ± 1.7% for experimental leather. In comparison to chrome-tanned leather, the experimental leathers were rated the highest in terms of dye fastness concerning rubbing action and against perspiration, showcasing the washable properties and better affinity and irreversible binding of dyes to the leather matrix. Mechanism studies through XPS spectroscopy revealed the interaction between the acidic amino acids of collagen and free zirconium metal sites and the imine linkage between amine pendants of MOF and basic amino acids of collagen protein. Further, the BOD5/COD ratio of 0.36 confirmed the better treatability of the wastewater emanating from the proposed process making it a sustainable tanning system. Thus, the combination of amine pendant MOFs with dialdehyde can be a promising strategy for the development of robust chrome-free leathers with excellent functional properties.

Double-Bridging Increases the Stability of Zinc(II) Metal-Organic Cages

A key feature of coordination cages is the dynamic nature of their coordinative bonds, which facilitates the synthesis of complex polyhedral structures and their post-assembly modification. However, this dynamic nature can limit cage stability. Increasing cage robustness is important for real-world use cases. Here we introduce a double-bridging strategy to increase cage stability, where designed pairs of bifunctional subcomponents combine to generate rectangular tetratopic ligands within pseudo-cubic Zn8L6 cages. These cages withstand transmetalation, the addition of competing ligands, and nucleophilic imines, under conditions where their single-bridged congeners decompose. Our approach not only increases the stability and robustness of the cages while maintaining their polyhedral structure, but also enables the incorporation of additional functional units in proximity to the cavity. The double-bridging strategy also facilitates the synthesis of larger cages, which are inaccessible as single-bridged congeners.

A Review of Metal-Organic Frameworks Derived Hollow-Structured Photocatalysts: Synthesis and Applications

Photocatalysis is a most important approach to addressing global energy shortages and environmental issues due to its environmentally friendly and sustainable properties. The key to realizing efficient photocatalysis relies on developing appropriate catalysts with high efficiency and chemical stability. Among various photocatalysts, Metal-organic frameworks (MOFs)-derived hollow-structured materials have drawn increased attention in photocatalysis based on advantages like more active sites, strong light absorption, efficient transfer of pho-induced charges, excellent stability, high electrical conductivity, and better biocompatibility. Specifically, MOFs-derived hollow-structured materials are widely utilized in photocatalytic CO2 reduction (CO2RR), hydrogen evolution (HER), nitrogen fixation (NRR), degradation, and other reactions. This review starts with the development story of MOFs, the commonly adopted synthesis strategies of MOFs-derived hollow materials, and the latest research progress in various photocatalytic applications are also introduced in detail. Ultimately, the challenges of MOFs-derived hollow-structured materials in practical photocatalytic applications are also prospected. This review holds great potential for developing more applicable and efficient MOFs-derived hollow-structured photocatalysts.

Ligand engineering enhances (photo) electrocatalytic activity and stability of zeolitic imidazolate frameworks via in-situ surface reconstruction

The current limitations in utilizing metal-organic frameworks for (photo)electrochemical applications stem from their diminished electrochemical stability. In our study, we illustrate a method to bolster the activity and stability of (photo)electrocatalytically active metal-organic frameworks through ligand engineering. We synthesize four distinct mixed-ligand versions of zeolitic imidazolate framework-67, and conduct a comprehensive investigation into the structural evolution and self-reconstruction during electrocatalytic oxygen evolution reactions. In contrast to the conventional single-ligand ZIF, where the framework undergoes a complete transformation into CoOOH via a stepwise oxidation, the ligand-engineered zeolitic imidazolate frameworks manage to preserve the fundamental framework structure by in-situ forming a protective cobalt (oxy)hydroxide layer on the surface. This surface reconstruction facilitates both conductivity and catalytic activity by one order of magnitude and considerably enhances the (photo)electrochemical stability. This work highlights the vital role of ligand engineering for designing advanced and stable metal-organic frameworks for photo- and electrocatalysis.

Tetraphenylethene-Based Ni8-Pyrazolate Metal-Organic Framework for Photoredox/Nickel Dual Catalysis of C-S Cross-Coupling

As a prototypical aggregation-induced emission luminogen (AIEgen), the tetraphenylethene (TPE) moiety has been judiciously modified as organic linkers for constructing various functional metal-organic frameworks (MOFs). However, these AIEgen-based MOFs have rarely received research attention in photocatalytic applications due to their limited stability in harsh reaction conditions. In this work, we report a robust Ni8-pyrazolate-based MOF (denoted as TPE4Pz-Ni) under the guidance of reticular chemistry, which is assembled by an AIE-active tetratopic linker of 1,1,2,2-tetrakis(4-(1H-pyrazol-4-yl)phenyl)ethane (H4-TPE4Pz) with a 12-connected Ni8-cluster of [Ni8(OH)4(H2O)2Pz12] (Pz = pyrazolate) in a (4,12)-connected ftw-a topological network. Notably, MOF TPE4Pz-Ni exhibits excellent stability in a wide range of solvents and even in a saturated NaOH solution. Moreover, its luminescent emission is effectively quenched via a ligand-to-metal charge transfer (LMCT) process originating from the TPE-cored linker to the Ni8 cluster, which enables TPE4Pz-Ni to act as an efficient photoredox/nickel dual catalyst for light-mediated C-S cross-coupling reactions between various aryl iodides and thiols.

Reversible Co(II)-Co(III) Transformation in a Family of Metal-Dipyrazolate Frameworks

Transformation between oxidation states is widespread in transition metal coordination chemistry and biochemistry, typically occurring in solution. However, air-induced oxidation in porous crystalline solids with retention of crystallinity is rare due to the dearth of materials with high structural stability that are inherently redox active. Herein, we report a new family of such materials, four isostructural cobalt-pyrazolate frameworks of face-centered cubic, fcu, topology, fcu-L-Co, that are sustained by Co8 molecular building blocks (MBBs) and dipyrazolate ligands, L. fcu-L-Co were observed to spontaneously transform from Co(II)8 to Co(III)8 MBBs in air with retention of crystallinity, marking the first such instance in metal-organic frameworks (MOFs). This transformation can also be achieved through water vapor sorption cycling, heating, or chemical oxidation. The reverse reactions were conducted by exposure of fcu-L-Co(III) to aqueous hydrazine. fcu-L-Co(II) exhibited high gravimetric water vapor uptakes of 0.55-0.68 g g-1 at 30% relative humidity (RH), while in fcu-L-Co(III) the inflection point shifted to lower RH and framework stability improved. Insight into the transformation between fcu-L-Co(II) and fcu-L-Co(III) was gained from single crystal X-ray diffraction and in situ spectroscopy. Overall, the crystal engineering approach we adopted has afforded a new family of MOFs that exhibit cobalt redox chemistry in a confined space coupled with high porosity.

Application of metal-organic framework materials in regenerative medicine

In the past few decades, scaffolds manufactured from composite or hybrid biomaterials of natural or synthetic origin have made great strides in enhancing wound healing and repairing fractures and pathological bone loss. However, the prevailing use of such scaffolds in tissue engineering is accompanied by numerous constraints, including low mechanical stability, poor biological activity, and impaired cell proliferation and differentiation. The performance of scaffolds in wound and bone tissue engineering may be enhanced by some modifications in the synthesis of nanoscale metal-organic framework (nano-MOF) scaffolds. Nano-MOFs have attracted researchers' attention in recent years due to their distinctive features, which include tenability, biocompatibility, good mechanical stability, and ultrahigh surface area. The biological properties of scaffolds are enhanced and tissue regeneration is facilitated by the introduction of nano-MOFs. Moreover, the physicochemical characteristics, drug loading, and ion release capacities of the scaffolds are improved by the nanoscale structure and topological features of nano-MOFs, which also control stem cell differentiation, proliferation, and attachment. This review provides further comprehensive detail about the most recent uses of nano-MOFs in tissue engineering. The distinct characteristics of nano-MOFs are explored in enhancing tissue repair, wound healing, osteoinduction, and bone conductivity. Significant attributes include high antibacterial activity, substantial drug-loading capacity, and the ability to regulate drug release. Finally, this discussion addresses the obstacles, clinical impediments, and considerations encountered in the application of these nanomaterials to diverse scaffolds, tissue-mimicking structures, dressings, fillers, and implants for bone tissue repair and wound healing.

Heavy Metal-Based Toxic Oxo-Pollutants Sequestration by Advanced Functional Porous Materials for Safe Drinking Water

ConspectusWater scarcity as a consequence of either environmental or economic actions is the most compelling global concern of the 21st century, as ∼2 billion people (26% of the total population) struggle to access safe drinking water and ∼3.6 billion (46% of the total population) lack access to clean water sanitation. In this context, groundwater pollution by toxic heavy metals and/or their oxo-pollutants, such as CrO42-, Cr2O72-, AsO43-, SeO32-, SeO42-, TcO4-, UO22+, etc., have been becoming rapidly growing global concerns. The severe toxicity upon bioaccumulation of these oxo-anions has prompted the US Environment Protection Agency (EPA) to mark these persistent and hazardous substances as priority pollutants. Additionally, the heavy-metal-based pollutants are difficult to transform into eco-friendly substances, thus presenting serious challenges toward human health and environmental preservation. To this end, the emergence of advanced functional porous materials (AFPMs), including metal-organic frameworks (MOFs), covalent organic frameworks (COFs), metal-organic polyhedrons (MOPs), porous organic polymers (POPs), etc., have presented extraordinary opportunities in material research and water treatment applications. The liberty in designing and structural tunability of AFPMs, facilitated by utilization of structure-encoded molecular building blocks, enables precise control over target-specificity and structure-property correlations. Bridging the gap between strategic material design and on-demand real-world application can facilitate the development of next-generation sorbents/ion-exchangers for efficient water treatment.In this Account, we summarize the recent advancements from our group toward the development of cutting-edge multifunctional ionic-porous sorbents, offering viable solutions toward providing clean and safe drinking water. Our vision allows us to comprehend this challenge through two strategic factors: efficient oxo-anion capture via ion-exchange and specific host-guest interactions via installation of modular functional groups. To provide an overview, we first highlight the different structural variants and coexistance of various toxic oxo-anions depending on the pH of the medium and their adverse effects. Next, we highlight the promising potential of water stable cationic MOFs toward selective remediation of toxic Cr(VI), Mn(VII), Tc(VI), Se(IV), Se(VI), U (VI), As(III), and As(V)-based toxic oxo-pollutants from water. In the subsequent sections, we summarize the target-specific design strategies and oxo-anion remediation performances of ionic porous organic polymers and hybrid functional porous materials. The key role of target-specific designability and/or structural fine-tuning of AFPMs toward preferential sorption of oxo-pollutants is systematically demonstrate. Particularly, the role of ion-exchange (anion-exchange) processes toward targeted oxo-pollutant capture by ionic AFPMs has been discussed in details. In several examples, the AFPMs were successful in reducing the toxic oxo-anion concentration levels lower than the permitted values for drinking water by the World Health Organizing Committee (WHO), showcasing their real-world applicability potency.Our contemporaneous endeavors in exploring ionic AFPMs for selective toxic oxo-anion sequestration may serve as a blueprint to researchers for future development of the next generation sorbent materials for energy-economically feasible water treatment methods.

Co-based metal-organic frameworks for enhanced nickel adsorption and its impact on nitrifying microbial activity

The release of nickel "Ni(II)" into aquatic environments is of great concern because of environmental and health issues. Metal-organic frameworks (MOFs) are one of the most promising technologies for removing heavy metals from water. In this work, an octahedral Co-based MOF (Co-MOF) was synthesized with a high Ni(II) removal capacity (qmax of 1534.09 ± 45.49 mg g-1) in aqueous media. For the first time, the effect of Co-MOF alone and in co-exposure with Ni(II) on nitrifying microbial consortium was assessed using dynamic microrespirometry. A single concentration of Co-MOF had no significant effects on nitrifying microbial consortium, while the concentration of Ni(II) exerted non-competitive inhibition on the nitrifying microbial consortium with an IC50 of 1.67 ± 0.03 mg L-1. In addition, the theoretical speciation analysis showed a decrease of 40% of IC50 when the free Ni(II) concentration was considered. Co-exposure of Co-MOF and Ni(II) during the nitrifying process allowed us to conclude that Co-MOF is an effective adsorbent for Ni(II) and can be used to mitigate the inhibitory effects of nickel on nitrifying microbial consortia, which is crucial for maintaining the good operation of wastewater treatment and balance of nitrogen cycle.

Recent Advances in the Synthesis and Application of Monolayer 2D Metal-Organic Framework Nanosheets

Monolayer 2D metal-organic framework (MOF) nanosheets, characterized by abundant exposed active sites and tunable structure and function (such as altering the metal nodes or organic ligands), have emerged as a pivotal class of 2D materials, demonstrating irreplaceable applications across diverse research domains in materials and chemistry. This review provides a comprehensive survey of the latest research progress in the synthesis of monolayer 2D MOF nanosheets. Specifically, recent synthetic strategies, including top-down and bottom-up methods, are delved and their applications in gas separation, catalysis, sensing platforms, and energy storage are explored. Additionally, the challenges faced in the investigation of monolayer 2D MOF nanosheets are elucidated and future opportunities for these materials as a novel generation of 2D materials are outlined.

Simultaneous capture of trace benzene and SO2 in a robust Ni(II)-pyrazolate framework

Benzene and SO2, coexisting as hazardous air pollutants in some cases, such as in coke oven emissions, have led to detrimental health and environmental effects. Physisorbents offer promise in capturing benzene and SO2, while their performance compromises at low concentration. Particularly, the simultaneous capture of trace benzene and SO2 under humid conditions is attractive but challenging. Here, we address this issue by constructing a robust pyrazolate metal-organic framework (MOF) sorbent featuring rich accessible Ni(II) sites with low affinity to water and good stability. This material achieves a high benzene uptake of 5.08 mmol g-1 at 10 Pa, surpassing previous benchmarks. More importantly, it exhibits an adsorption capacity of ~0.51 mmol g-1 for 10 ppm benzene and ~1.21 mmol g-1 for 250 ppm SO2 under 30% relative humidity. This work demonstrates that a pioneering MOF enables simultaneous capture of trace benzene and SO2, highlighting the potential of physisorbents for industrial effluent remediation, even in the presence of moisture.

Leveraging Isoreticular Principle to Elucidate the Key Role of Inherent Hydrogen-Bonding Anchoring Sites in Enhancing Water Sorption Cyclability of Zr(IV) Metal-Organic Frameworks

Water adsorption/desorption cyclability of porous materials is a prerequisite for diverse applications, including atmospheric water harvesting (AWH), humidity autocontrol (HAC), heat pumps and chillers, and hydrolytic catalysis. However, unambiguous molecular insights into the correlation between underlying building blocks and the cyclability are still highly elusive. In this work, by taking advantage of the well-established isoreticular synthetic principle in Zr(IV) metal-organic frameworks (Zr-MOFs), we show that the inherent density of hydrogen atoms in the organic skeleton can play a key role in regulating the water sorption cyclability of MOFs. The ease of isoreticular practice of Zr-MOFs enables the successful syntheses of two pairs of isostructural Zr-MOFs (NU-901 and NU-903, NU-950 and SJTU-9) from pyrene- or benzene-cored carboxylate linkers, which feature scu and sqc topological nets, respectively. NU-901 and NU-950 comprised of pyrene skeletons carrying more hydrogen-bonding anchoring sites show distinctly inferior cyclability as compared with NU-903 and SJTU-9 built of benzene units. Single-crystal X-ray crystallography analysis of the hydrated structure clearly unveils the water molecule-involved interactions with the hydrogen-bonding donors of benzene moieties. Remarkably, NU-903 and SJTU-9 isomers exhibit outstanding water vapor sorption capacities as well as working capacities at the desired humidity range with potential implementations covering indoor humidity control and water harvesting. Our findings uncover the importance of hydrogen-bonding anchoring site engineering of organic scaffold in manipulating the framework durability toward water sorption cycle and will also likely facilitate the rational design and development of highly robust porous materials.

Signal-On Detection of Caspase-3 with Methylene Blue-Loaded Metal-Organic Frameworks as Signal Reporters

In this work, we report on an electrochemical method for the signal-on detection of caspase-3 and the evaluation of apoptosis based on the biotinylation reaction and the signal amplification of methylene blue (MB)-loaded metal-organic frameworks (MOFs). Zr-based UiO-66-NH2 MOFs were used as the nanocarriers to load electroactive MB molecules. Recombinant hexahistidine (His6)-tagged streptavidin (rSA) was attached to the MOFs through the coordination interaction between the His6 tag in rSA and the metal ions on the surface of the MOFs. The acetylated peptide substrate Ac-GDEVDGGGPPPPC was immobilized on the gold electrode. In the presence of caspase-3, the peptide was specifically cleaved, leading to the release of the Ac-GDEVD sequence. A N-terminal amine group was generated and then biotinylated in the presence of biotin-NHS. Based on the strong interaction between rSA and biotin, rSA@MOF@MB was captured by the biotinylated peptide-modified electrode, producing a significantly amplified electrochemical signal. Caspase-3 was sensitively determined with a linear range from 0.1 to 25 pg/mL and a limit of detection down to 0.04 pg/mL. Further, the active caspase-3 in apoptosis inducer-treated HeLa cells was further quantified by this method. The proposed signal-on biosensor is compatible with the complex biological samples and shows great potential for apoptosis-related diagnosis and the screening of caspase-targeting drugs.

Metal-Organic Framework Stability in Water and Harsh Environments from Data-Driven Models Trained on the Diverse WS24 Data Set

Metal-organic frameworks (MOFs) are porous materials with applications in gas separations and catalysis, but a lack of water stability often limits their practical use given the ubiquity of water. Consequently, it is useful to predict whether a MOF is water-stable before investing time and resources into synthesis. Existing heuristics for designing water-stable MOFs lack generality and limit the diversity of explored chemistry due to narrowly defined criteria. Machine learning (ML) models offer the promise to improve the generality of predictions but require data. In an improvement on previous efforts, we enlarge the available training data for MOF water stability prediction by over 400%, adding 911 MOFs with water stability labels assigned through semiautomated manuscript analysis to curate the new data set WS24. The additional data are shown to improve ML model performance (test ROC-AUC > 0.8) over diverse chemistry for the prediction of both water stability and stability in harsher acidic conditions. We illustrate how the expanded data set and models can be used with a previously developed activation stability model in combination with genetic algorithms to quickly screen ∼10,000 MOFs from a space of hundreds of thousands for candidates with multivariate stability (upon activation, in water, and in acid). We uncover metal- and geometry-specific design rules for robust MOFs. The data set and ML models developed in this work, which we disseminate through an easy-to-use web interface, are expected to contribute toward the accelerated discovery of novel, water-stable MOFs for applications such as direct air gas capture and water treatment.

Advances in Functionalized Biocomposites of Living Cells Combined with Metal-Organic Frameworks

Motivated by the remarkable innate characteristics of cells in living organisms, we have found that hybrid materials that combine bioorganisms with nanomaterials have significantly propelled advancements in industrial applications. However, the practical deployment of unmodified living entities is inherently limited due to their sensitivity to environmental fluctuations. To surmount these challenges, an efficacious strategy for the biomimetic mineralization of living organisms with nanomaterials has emerged, demonstrating extraordinary potential in biotechnology. Among them, innovative composites have been engineered by enveloping bioorganisms with a metal-organic framework (MOF) coating. This review systematically summarizes the latest developments in living cells/MOF-based composites, detailing the methodologies employed in structure fabrication and their diverse applications, such as bioentity preservation, sensing, catalysis, photoluminescence, and drug delivery. Moreover, the synergistic benefits arising from the individual compounds are elucidated. This review aspires to illuminate new prospects for fabricating living cells/MOF composites and concludes with a perspective on the prevailing challenges and impending opportunities for future research in this field.

Defect-engineered chiral metal-organic frameworks

Chirality has an important impact on chemical and biological research, as most active substances are chiral. In recent decades, metal-organic frameworks (MOFs), which are assembled from metal ions or clusters and organic linkers via metal-ligand bonding, have attracted considerable scientific interest due to their high crystallinity, exceptional porosity and tunable pore sizes, high modularity, and diverse functionalities. Since the discovery of the first functional chiral metal-organic frameworks (CMOFs), CMOFs have been involved in a variety of disciplines such as chemistry, physics, optics, medicine, and pharmacology. The introduction of defect engineering theory into CMOFs allows the construction of a class of defective CMOFs with high hydrothermal stability and multi-stage pore structure. The introduction of defects not only increases the active sites but also enlarges the pore sizes of the materials, which improves chiral recognition, separation, and catalytic reactions, and has been widely investigated in various fields. This review describes the design and synthesis of various defective CMOFs, their characterization, and applications. Finally, the development of the materials is summarized, and an outlook is given. This review should provide researchers with an insight into the design and study of complex defective CMOFs.

Evaluation of Open-Source Large Language Models for Metal-Organic Frameworks Research

Along with the development of machine learning, deep learning, and large language models (LLMs) such as GPT-4 (GPT: Generative Pre-Trained Transformer), artificial intelligence (AI) tools have been playing an increasingly important role in chemical and material research to facilitate the material screening and design. Despite the exciting progress of GPT-4 based AI research assistance, open-source LLMs have not gained much attention from the scientific community. This work primarily focused on metal-organic frameworks (MOFs) as a subdomain of chemistry and evaluated six top-rated open-source LLMs with a comprehensive set of tasks including MOFs knowledge, basic chemistry knowledge, in-depth chemistry knowledge, knowledge extraction, database reading, predicting material property, experiment design, computational scripts generation, guiding experiment, data analysis, and paper polishing, which covers the basic units of MOFs research. In general, these LLMs were capable of most of the tasks. Especially, Llama2-7B and ChatGLM2-6B were found to perform particularly well with moderate computational resources. Additionally, the performance of different parameter versions of the same model was compared, which revealed the superior performance of higher parameter versions.

Metal-Organic-Frameworks Based Mixed-Matrix Membranes for CO2 Separation: An Applicable-Conceptual Approach

A promising class of porous crystalline materials, metal-organic frameworks (MOFs), have recently emerged as a potential material in fabricating mixed matrix membranes (MMMs) for gas separation applications. Their unique chemistry and structural versatility offer substantial advantages over conventional fillers. This review gives an in-depth exploration of MOF chemistry, focusing on strategies to manipulate their adsorption behavior to enhance separation properties. We scrutinize the impact of various MOF-based MMM components, including polymer matrix, MOFs fillers and polymer/filler interface, on the overall gas separation performance. This involves a detailed analysis of key parameters associated with MMM preparation. Additionally, we offer a comprehensive overview of the determining factors in MOF-based MMM development for gas separation, including MOF structure, synthesis, and chemistry. Moreover, the most advances in modification strategies of MOF for CO2 separation, such as a wide variety of hybrid MOFs will be outlined, which opens the door to an improved CO2 separation process. Finally, the gas transport mechanisms of MMMs are thoroughly discussed to understand the factors affecting the gas permeation through the polymer matrix, MOFs and interface between them.

Central Metal-Triggered Structural Transformation of a 2D Layered MOF: Mechanistic Studies and Applications

The structural transformation of metal-organic frameworks (MOFs) has attracted increasing interests, which has not only produced various new structures but also served as a fantastic platform for MOF-based kinetic analysis. Multiple reaction conditions have been documented to cause structural transformation; nevertheless, central metal-induced topological alteration of MOFs is rare. Herein, we reported a structural transformation of a 2D layered Cd-MOF driven by Cd(II) ions. After being submerged in the aqueous solution of cadmium nitrate, the twofold interpenetrated 2D network of [Cd(hsb-2)(bdc)·5H2O]n [HSB-W10; bdc: 1,4-benzenedicarboxylate; hsb-2:1,2-bis(4'-pyridylmethylamino)-ethane] was converted into a novel noninterpenetrated 2D network [Cd1.5(hsb-2)(bdc)1.5(H2O)2·H2O]n (HSB-W16). This partial dissolution-recrystallization process was investigated by integrating controlled experiments, 1H NMR spectra, and photographic tracking analysis. Furthermore, a novel strategy combining in situ multicomponent dye encapsulation and central metal-triggered structural transformation was developed for the fabrication of MOF materials with white-light emission. By adopting this strategy, different dye guest molecules were concurrently introduced into the HSB-W16 host matrix, leading to a range of white-light-emitting MOF composites. This work will enable detailed studies of solid-state transformations and demonstrate a promising application prospect for structural transformation.

Metalation of metal-organic frameworks: fundamentals and applications

Metalation of metal-organic frameworks (MOFs) has been developed as a prominent strategy for materials functionalization for pore chemistry modulation and property optimization. By introducing exotic metal ions/complexes/nanoparticles onto/into the parent framework, many metallized MOFs have exhibited significantly improved performance in a wide range of applications. In this review, we focus on the research progress in the metalation of metal-organic frameworks during the last five years, spanning the design principles, synthetic strategies, and potential applications. Based on the crystal engineering principles, a minor change in the MOF composition through metalation would lead to leveraged variation of properties. This review starts from the general strategies established for the incorporation of metal species within MOFs, followed by the design principles to graft the desired functionality while maintaining the porosity of frameworks. Facile metalation has contributed a great number of bespoke materials with excellent performance, and we summarize their applications in gas adsorption and separation, heterogeneous catalysis, detection and sensing, and energy storage and conversion. The underlying mechanisms are also investigated by state-of-the-art techniques and analyzed for gaining insight into the structure-property relationships, which would in turn facilitate the further development of design principles. Finally, the current challenges and opportunities in MOF metalation have been discussed, and the promising future directions for customizing the next-generation advanced materials have been outlined as well.

Electrochemical sensing mechanisms of neonicotinoid pesticides and recent progress in utilizing functional materials for electrochemical detection platforms

The excessive residue of neonicotinoid pesticides in the environment and food poses a severe threat to human health, necessitating the urgent development of a sensitive and efficient method for detecting trace amounts of these pesticides. Electrochemical sensors, characterized by their simplicity of operation, rapid response, low cost, strong selectivity, and high feasibility, have garnered significant attention for their immense potential in swiftly detecting trace target molecules. The detection capability of electrochemical sensors primarily relies on the catalytic activity of electrode materials towards the target analyte, efficient loading of biomolecular functionalities, and the effective conversion of interactions between the target analyte and its receptor into electrical signals. Electrode materials with superior performance play a crucial role in enhancing the detection capability of electrochemical sensors. With the continuous advancement of nanotechnology, particularly the widespread application of novel functional materials, there is paramount significance in broadening the applicability and expanding the detection range of pesticide sensors. This comprehensive review encapsulates the electrochemical detection mechanisms of neonicotinoid pesticides, providing detailed insights into the outstanding roles, advantages, and limitations of functional materials such as carbon-based materials, metal-organic framework materials, supramolecular materials, metal-based nanomaterials, as well as molecular imprinted materials, antibodies/antigens, and aptamers as molecular recognition elements in the construction of electrochemical sensors for neonicotinoid pesticides. Furthermore, prospects and challenges facing various electrochemical sensors based on functional materials for neonicotinoid pesticides are discussed, providing valuable insights for the future development and application of biosensors for simplified on-site detection of agricultural residues.

Metal-organic framework (MOF)/C-dots and covalent organic framework (COF)/C-dots hybrid nanocomposites: Fabrications and applications in sensing, medical, environmental, and energy sectors

Developing new hybrid materials is critical for addressing the current needs of the world in various fields, such as energy, sensing, health, hygiene, and others. C-dots are a member of the carbon nanomaterial family with numerous applications. Aggregation is one of the barriers to the performance of C-dots, which causes luminescence quenching, surface area decreases, etc. To improve the performance of C-dots, numerous matrices including metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), and polymers have been composited with C-dots. The porous crystalline structures, which are constituents of metal nodes and organic linkers (MOFs) or covalently attached organic units (COFs) provide privileged features such as high specific surface area, tunable structures, and pore diameters, modifiable surface, high thermal, mechanical, and chemical stabilities. Also, the MOFs and COFs protect the C-dots from the environment. Therefore, MOF/C-dots and COF/C-dots composites combine their features while retaining topological properties and improving performances. In this review, we first compare MOFs with COFs as matrices for C-dots. Then, the recent progress in developing hybrid MOFs/C-dots and COFs/C-dots composites has been discussed and their applications in various fields have been explained briefly.

Microwave-assisted synthesis of novel Ti/BTB-MOFs as porous anticancer and antibacterial agents

Nano compounds, especially metal-organic frameworks (MOFs), have significant properties. Among the most important properties of these compounds, which depend on their specific surface area and porosity, are biological properties, such as anticancer and antibacterial properties. In this study, a new titanium/BTB metal-organic framework (Ti/BTB-MOF) was synthesized by using titanium nitrate and 1,3,5-Tris(4-carboxyphenyl)benzene (BTB) under microwave radiation. The structure of the synthesized Ti/BTB-MOF was characterized and confirmed using X-ray diffraction (XRD) patterns, X-ray photoelectron spectroscopy (XPS) analysis, Fourier transform infrared (FT-IR) spectra, energy-dispersive X-ray (EDAX) analysis mapping, scanning electron microscope (SEM) images, thermogravimetric analysis (TGA) curves, and Brunauer-Emmett-Teller (BET) analysis. The in vitro anticancer properties of Ti/BTB-MOF were evaluated using the MTT method against MG-63/bone cancer cells and A-431/skin cancer cells. The in vitro antibacterial activity was tested using the Clinical and Laboratory Standards Institute (CLSI) guidelines. In the anticancer activity, IC50 (half-maximal inhibitory concentration) values of 152 μg/mL and 201 μg/mL for MG-63/bone cancer cells and A-431/skin cancer cells, respectively, were observed. In the antibacterial activity, minimum inhibitory concentrations (MICs) of 2-64 μg/mL were observed against studied pathogenic strains. The antimicrobial activity of Ti/BTB-MOF was higher than that of penicillin and gentamicin. Therefore, the synthesized Ti/BTB-MOF could be introduced as a suitable bioactive candidate.

Enabling C2H2/CO2 Separation Under Humid Conditions with a Methylated Copper MOF

As a unique subclass of metal-organic frameworks (MOFs), MOFs with open metal site (OMS) are demonstrated efficient gas separation performance through pi complexation with unsaturated hydrocarbons. However, their practical application faces the challenge of humidity that causes structure degradation and completive binding at the OMS. In this work, the effect of linker methylation of a copper MOF (BUT-155) on the C2H2/CO2 separation performance under humid condition is evaluated. The water adsorption isotherm, adsorption kinetics, and breakthrough under dry and humid conditions are performed. The BUT-155 with methylated linker exhibits lower water uptake and adsorption kinetics under humid condition (RH = 20%), in comparison with HKUST-1. Therefore, the C2H2/CO2 separation performance of BUT-155 is much less affected by water, especially under higher gas flow rate. Moreover, the dynamic C2H2/CO2 separation performance of BUT-155 can maintain five breakthrough cycles under humid conditions (RH = 20% and RH = 80%) without obvious performance degradation.

A biomimetic camouflaged metal organic framework for enhanced siRNA delivery in the tumor environment

Gene silencing through RNA interference (RNAi), particularly using small double-stranded RNA (siRNA), has been identified as a potent strategy for targeted cancer treatment. Yet, its application faces challenges such as nuclease degradation, inefficient cellular uptake, endosomal entrapment, off-target effects, and immune responses, which have hindered its effective delivery. In the past few years, these challenges have been addressed significantly by using camouflaged metal-organic framework (MOF) nanocarriers. These nanocarriers protect siRNA from degradation, enhance cellular uptake, and reduce unintended side effects by effectively targeting desired cells while evading immune detection. By combining the properties of biomimetic membranes and MOFs, these nanocarriers offer superior benefits such as extended circulation times, enhanced stability, and reduced immune responses. Moreover, through ligand-receptor interactions, biomimetic membrane-coated MOFs achieve homologous targeting, minimizing off-target adverse effects. The MOFs, acting as the core, efficiently encapsulate and protect siRNA molecules, while the biomimetic membrane-coated surface provides homologous targeting, further increasing the precision of siRNA delivery to cancer cells. In particular, the biomimetic membranes help to shield the MOFs from the immune system, avoiding unwanted immune responses and improving their biocompatibility. The combination of siRNA with innovative nanocarriers, such as camouflaged-MOFs, presents a significant advancement in cancer therapy. The ability to deliver siRNA with precision and effectiveness using these camouflaged nanocarriers holds great promise for achieving more personalized and efficient cancer treatments in the future. This review article discusses the significant progress made in the development of siRNA therapeutics for cancer, focusing on their effective delivery through novel nanocarriers, with a particular emphasis on the role of metal-organic frameworks (MOFs) as camouflaged nanocarriers.

Rare-Earth Metal-Organic Framework with Nonplanar Porphyrin Groups for High-Efficiency Photocatalysis

Nonplanar porphyrins play crucial roles in many biological processes and chemical reactions as catalysts. However, the preparation of artificial nonplanar porphyrins suffers from complicated organic syntheses. Herein, we present a new rare-earth porphyrinic metal-organic framework (RE-PMOF), BUT-233, which is a three-dimensional (3D) framework structure with the flu topology consisting of 4-connected BBCPPP-Ph ligands H4BBCPPP-Ph = 5',5⁗-(10,20-diphenylporphyrin-5,15-diyl)bis([1,1':3',1″-terphenyl]-4,4'' dicarboxylic acid) and 8-connected Eu6 clusters. Noteworthily, the porphyrin cores of the BBCPPP-Ph ligands in BUT-233 are nonplanar with a ruffle-like conformation. In contrast, the porphyrin core in the free ligand H4BBCPPP-Ph is in a nearly ideally planar conformation, as confirmed by its single-crystal structure. BUT-233 is microporous with 6-8 Å pores and a Brunauer-Emmett-Teller (BET) surface area of 649 m2/g, as well as high stability in common solvents. The MOF was used as a photocatalyst for the oxidation degradation of a chemical warfare agent model molecule CEES (CEES = 2-chloroethyl ethyl sulfide) under the light-emitting diode (LED) irradiation and an O2 atmosphere at room temperature. CEES was almost completely converted into its nontoxic light-oxidized product CEESO (CEESO = 2-chloroethyl ethyl sulfoxide) in only 5 min with t1/2 = 2 min (t1/2: half-life). Moreover, the toxic deep-oxidized product 2-chloroethyl ethyl sulfone (CEESO2) was not detected. The catalytic activity of BUT-233 was high in comparison with those of some previously reported MOF catalysts. The results of photo/electrochemical property studies suggested that the high catalytic activity of BUT-233 was benefited from the presence of nonplanar porphyrin rings on its pore surface.